Pasteur made simple – mechanochemical transformation of racemic amino acid crystals into racemic conglomerate crystals

Racemic compounds of proteinogenic amino acids valine, leucine and isoleucine were transformed to their corresponding conglomerates via a metal-mediated mechanochemical process.

Screw sense alone can govern enantioselective extension of a helical peptide by kinetic resolution of a racemic amino acid

Helical secondary structure alone, even in the absence of local chiral residues, can direct the enantioselectivity of peptide coupling.

Redetermined crystal structure of α-DL-methionine at 340 K

Two forms, α and β, are known for the racemic amino acid DL-methionine, C5H11NO2S. The phase transition between them, taking place around 326 K, is associated with sliding at the central interfaces of the hydrophobic regions in the crystal, leaving the hydrogen-bonding pattern unperturbed. For the high-temperature α phase, only a structure of rather low quality has been available [Rfactor = 0.118, no H-atom coordinates; Taniguchiet al.(1980).Bull. Chem. Soc. Jpn,53, 803–804]. We here present accurate structural data for this polymorph [R(F) = 0.049], which are compared with other related amino acid structures with similar properties. We report for the first time that the side chain of this phase has a minor disorder component [occupancy 0.0491 (18)] with agauche+ rather than agauche− conformation for the N—C—C—C group. In the crystal of the title compound, N—H...O hydrogen bonds link the molecules into (100) sheets.

A new synthetic protocol for coumarin amino acid

The hydrochloride of the racemic amino acid (2-(7-hydroxycoumarin-4-yl)ethyl)glycine, which can serve as a fluorescent probe in proteins, and two halogen derivatives of it, were synthesized by using a new synthetic protocol in five steps. It is less costly and relatively easy to prepare this kind of fluorescent amino acid with the new synthetic method. Furthermore, it can be applied to synthesize other derivatives of the coumarin amino acid with some specific properties.

Chitin Nanofiber Membranes for Chiral Separation

Nanofiber membranes for chiral separation were prepared from chitin, which is the most abundant natural amino polysaccharide. The membrane showed chiral separation ability by adopting concentration gradient as a driving force for membrane transport. In other words, the chitin nanofiber membrane selectively transported the D-isomer of glutamic acid (Glu), phenylalanine (Phe), and lysine (Lys) from the corresponding racemic amino acid mixtures.